Add Gemini CLI adapter

[wazionapps]

Overview

NEXO currently works natively with Claude Code via CLAUDE.md + MCP. Extending support to Gemini CLI would open NEXO to the growing community of Gemini users and significantly expand our audience.

What this involves

Gemini CLI supports a GEMINI.md file (analogous to CLAUDE.md) and its own tool/extension system. An adapter would:

1. Create GEMINI.md template — translate NEXO's startup protocol, heartbeat loop, and guard rules into Gemini CLI's instruction format
2. Map MCP tool calls — Gemini CLI has its own extension mechanism; the adapter needs to route nexo_* calls through it
3. Document differences — startup phase, session handling, and context window behavior differ between Claude Code and Gemini CLI

Acceptance criteria

• adapters/gemini/GEMINI.md template that mirrors src/CLAUDE.md startup protocol
• adapters/gemini/README.md with step-by-step setup guide
• Document which NEXO features are fully supported, partially supported, and not yet supported
• Tested against Gemini CLI locally (basic startup + heartbeat flow)

Good starting points

• Read src/CLAUDE.md to understand the current Claude Code protocol
• Read src/nexo-mcp/server.py to understand the MCP tool surface
• Gemini CLI docs: https://github.com/google-gemini/gemini-cli

Why this matters

NEXO's memory architecture (Atkinson-Shiffrin, Ebbinghaus decay, RAG) is model-agnostic. The MCP server runs locally regardless of which AI client connects. An adapter is mostly about translation — not rebuilding core logic.

This is a great first contribution: it touches documentation, config templates, and light integration work. No changes to the core MCP server required.

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